Re: [lockdep] b09be676e0 BUG: unable to handle kernel NULL pointer dereference at 000001f2

[Fengguang Wu]

On Thu, Oct 12, 2017 at 10:47:25AM +0200, Peter Zijlstra wrote:
> On Tue, Oct 03, 2017 at 10:06:34PM +0800, Fengguang Wu wrote:
>
> > #!/bin/bash
> >
> > kernel=$1
> > initrd=openwrt-trinity-i386.cgz
> >
> > wget --no-clobber https://github.com/fengguang/reproduce-kernel-bug/raw/master/initrd/$initrd
> >
> > kvm=(
> > 	qemu-system-x86_64
> > 	-enable-kvm
> > 	-cpu Haswell,+smep
> > 	-kernel $kernel
> > 	-initrd $initrd
> > 	-m 256
> > 	-smp 1
> > 	-device e1000,netdev=net0
> > 	-netdev user,id=net0
> > 	-boot order=nc
> > 	-no-reboot
> > 	-watchdog i6300esb
> > 	-watchdog-action debug
> > 	-rtc base=localtime
> > 	-serial stdio
> > 	-display none
> > 	-monitor null
> > )
> >
> > append=(
> > 	root=/dev/ram0
> > 	hung_task_panic=1
> > 	debug
> > 	apic=debug
> > 	sysrq_always_enabled
> > 	rcupdate.rcu_cpu_stall_timeout=100
> > 	net.ifnames=0
> > 	printk.devkmsg=on
> > 	panic=-1
> > 	softlockup_panic=1
> > 	nmi_watchdog=panic
> > 	oops=panic
> > 	load_ramdisk=2
> > 	prompt_ramdisk=0
> > 	drbd.minor_count=8
> > 	systemd.log_level=err
> > 	ignore_loglevel
> > 	console=tty0
> > 	earlyprintk=ttyS0,115200
> > 	console=ttyS0,115200
> > 	vga=normal
> > 	rw
> > 	drbd.minor_count=8
> > )
> >
> > "${kvm[@]}" -append "${append[*]}"
>
>
> So I was wanting to go chase that one splat you triggered, but the above
> (after s/Haswell,+smep/host/) boots right up until it wants an init:
>
> [    0.000000] Kernel command line: root=/dev/ram0 hung_task_panic=1 debug apic=debug sysrq_always_enabled rcupdate.rcu_cpu_stall_timeout=100 net.ifnames=0 printk.devkmsg=on panic=-1 softlockup_panic=1 nmi_watchdog=panic oops=panic load_ramdisk=2 prompt_ramdisk=0 drbd.minor_count=8 systemd.log_level=err ignore_loglevel console=tty0 earlyprintk=ttyS0,115200 console=ttyS0,115200 vga=normal rw drbd.minor_count=8
>
> [   35.721719] Kernel panic - not syncing: No working init found.  Try passing init= option to kernel. See Linux Documentation/admin-guide/init.rst for guidance.

Well I got the same result. The script and initrd image matches well
with my local version. I'll dig what goes wrong.

> And it did download that initrd thingy...
>
> $ shasum openwrt-trinity-i386.cgz
> 0a405d02a162defd82a5ffd556fd24e0ee2f994a  openwrt-trinity-i386.cgz
>
>
> Anything else I need?